Synergistic cavity-enhanced photoresponse in transition metal dichalcogenide heterostructures

The inherently low optical absorption of atomically thin semiconductors presents a fundamental obstacle for realizing high-efficiency two-dimensional (2D) optoelectronic devices. While van der Waals (vdWs) heterostructures and optical cavities have individually shown promise in addressing this limitation, their combined potential remains largely unexplored. Here, a synergistic approach is realized by integrating MoS2/SnSe2 heterostructure with an asymmetric Fabry–Pérot (F-P) cavity substrate, enabling unprecedented photoresponse enhancement. The carefully engineered type II band alignment along with large band offset facilitates efficient charge separation, while the F-P cavity significantly enhances the optical absorption. As a result, a high-performance photodetector based on the MoS2/SnSe2 heterostructure is demonstrated operating across a broad spectral range (450–900 nm). At 450 nm wavelength and Vds = 2 V, the device achieves an ultrahigh responsivity of 4.7 × 103 AW−1, surpassing previously reported 2D materials-based cavity photodetectors while maintaining a fast response speed of 150 ms. The external quantum efficiency, and detectivity at 450 nm are 1.3 × 106 % and 1.8 × 1014 Jones, respectively. Moreover, the device also operates efficiently under zero bias due to the built-in electric field at the interface, making it suitable for low-power applications. This study shows a promising path toward overcoming the low optical absorption of atomically thin materials.